Re: [Google/gcc-4_9][PATCH][target/x86_64] PR 63538

[Sriraman Tallam <tmsriram@google.com>]

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On Mon, Oct 20, 2014 at 12:59 PM, Xinliang David Li <davidxl@google.com> wrote:
> On Mon, Oct 20, 2014 at 11:59 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>> On Mon, Oct 20, 2014 at 10:51 AM, Andrew Pinski <pinskia@gmail.com> wrote:
>>> On Mon, Oct 20, 2014 at 10:46 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>> On Mon, Oct 20, 2014 at 10:42 AM, Xinliang David Li <davidxl@google.com> wrote:
>>>>> Why removing the tree_code check?
>>>>
>>>> The actual problem happens because STRING_CSTs (end up in .lrodata)
>>>> are not set a far address as they dont match the VAR_DECL check here.
>>>> Futher,  "ix86_in_large_data_p" call has the TREE_CODE check to do the
>>>> right thing so this seems unnecessary & buggy here.
>>>
>>> I think he is asking because TREE_STATIC (decl) || DECL_EXTERNAL
>>> (decl) might be an issue for STRING_CSTs.
>>
>> TREE_STATIC is true for STRING_CSTs and DECL_EXTERNAL false, that looks ok.
>
> The values for STRING_CST make sense, but it is not documented in
> tree.h for use with STRING_CST. Maybe do this:
>
>  if (((TREE_CODE (decl) == VAR_DECL&& (TREE_STATIC (decl) ||
> DECL_EXTERNAL (decl))
>        ||TREE_CODE (decl) == STRING_CST)
>       && ix86_in_large_data_p (decl))
>
> which can be simplified to:
>
>  if ((TREE_CODE (decl) == VAR_DECL && is_global_var (decl) ||TREE_CODE
> (decl) == STRING_CST)
>   && ix86_in_large_data_p (decl))

Patch updated.

Thanks
Sri

>      ...
>
> David
>>
>> Thanks
>> Sri
>>
>>>
>>> Thanks,
>>> Andrew
>>>
>>>
>>>>
>>>> Thanks
>>>> Sri
>>>>
>>>>>
>>>>> David
>>>>>
>>>>> On Mon, Oct 20, 2014 at 10:35 AM, Sriraman Tallam <tmsriram@google.com> wrote:
>>>>>> Hi,
>>>>>>
>>>>>>    This patch is under review for trunk GCC :
>>>>>> https://gcc.gnu.org/ml/gcc-patches/2014-10/msg01638.html.
>>>>>>
>>>>>>     In the mean time, is this ok for google/gcc-4_9 branch?  Without
>>>>>> this, -mcmodel=medium is unusable if .lrodata goes beyond the 2G
>>>>>> boundary.
>>>>>>
>>>>>> Thanks
>>>>>> Sri

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Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c	(revision 216287)
+++ config/i386/i386.c	(working copy)
@@ -41331,8 +41331,8 @@ ix86_encode_section_info (tree decl, rtx rtl, int
 {
   default_encode_section_info (decl, rtl, first);
 
-  if (TREE_CODE (decl) == VAR_DECL
-      && (TREE_STATIC (decl) || DECL_EXTERNAL (decl))
+  if (((TREE_CODE (decl) == VAR_DECL && is_global_var (decl))
+       || TREE_CODE(decl) == STRING_CST)
       && ix86_in_large_data_p (decl))
     SYMBOL_REF_FLAGS (XEXP (rtl, 0)) |= SYMBOL_FLAG_FAR_ADDR;
 }
Index: testsuite/gcc.dg/pr63538.c
===================================================================
--- testsuite/gcc.dg/pr63538.c	(revision 0)
+++ testsuite/gcc.dg/pr63538.c	(revision 0)
@@ -0,0 +1,14 @@
+/* PR63538 is about not using 64-bit addresses for .lrodata accesses when it
+   involves STRING_CSTs.  */
+/* { dg-do compile { target x86_64-*-* } } */
+/* { dg-options "-O2 -mcmodel=medium -mlarge-data-threshold=0" { target x86_64-*-* } } */
+
+#include <stdio.h>
+
+const char *str = "Hello World";
+
+int main() {
+ printf("str = %p %s\n",str, str);
+ return 0;
+}
+/* { dg-final { scan-assembler-not "movl" } } */